Office of Environmental Health Hazard Assessment

Pesticides and Proposition 65

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What is Proposition 65?

Proposition 65, officially known as the "Safe Drinking Water and Toxic Enforcement Act," was approved by California voters in 1986. Proposition 65 is based on the premise that the public and workers have a right to be informed about exposures to chemicals that are known to the state to cause cancer, birth defects, or other reproductive harm.

The California Environmental Protection Agency's Office of Environmental Health Hazard Assessment (OEHHA) is the lead agency responsible for carrying out Proposition 65. OEHHA gets input and comments from the Department of Pesticide Regulation (DPR), other agencies, and interested parties to ensure the "best scientific" information is used in listing chemicals. For additional information on OEHHA's implementation of Proposition 65, visit OEHHA's Web site at, then click on Proposition 65, or call (916) 445-6900.

What does Proposition 65 require?

Proposition 65 requires the Governor to maintain and publish a list of chemicals that are known to the state to cause cancer, birth defects, or other reproductive harm. The list, which must be updated at least once a year, covers a wide range of chemicals which are sometimes in products we use, such as dyes, solvents, drugs, food additives, by-products of certain processes, and pesticides. Some of these chemicals are naturally occurring, some are added to common household products, and some are used only in specific industrial applications.

Pesticides on Proposition 65 List, PDF (216 kb) - Updated May 2018

How do pesticides get listed?

Chemicals - including pesticides - may be put on the Proposition 65 list in any one of three ways:

  • The Governor has appointed two scientific committees to determine if a pesticide or other chemicals has clearly been shown to cause cancer, birth defects, or other reproductive harm. One committee is responsible for reviewing data for cancer-related information, and the other committee is responsible for reviewing data for developmental and reproductive toxicity. The committees consider chemicals for listing in public meetings held at least once a year.
  • If a state or federal agency formally requires that a pesticide be labeled or identified as causing cancer or reproductive toxicity, it must be listed under Proposition 65 as well.
  • The scientific committees, consisting of members appointed by the Governor, also designate other entities, whose decisions are authoritative in these areas. For carcinogenicity, the designated authorities are the U.S. Environmental Protection Agency (U.S. EPA), U.S. Food and Drug Administration (U.S. FDA), National Institute for Occupational Safety and Health (NIOSH), National Toxicology Program (NTP), and the International Agency for Research on Cancer (IARC). For reproductive toxicity, the designated authorities are the U.S. EPA, U.S. FDA, NIOSH, and IARC (for transplacental carcinogenicity only). If any of the state's designated "authoritative" bodies formally identifies a pesticide as causing cancer or reproductive toxicity that pesticide must be listed under Proposition 65, if all the pertinent scientific and regulatory criteria are met. In addition, Proposition 65 requires the listing of substances identified by reference as causing cancer or reproductive toxicity in Labor Code section 6382(b)(1), and Labor Code section 6382(d). These sections refer to substances identified as human or animal carcinogens by IARC, and substances identified as carcinogens or potential carcinogens by IARC or NTP.

What are the responsibilities when using a listed pesticide?

Twelve months after a chemical, such as a pesticide, is added to the Proposition 65 chemical list, businesses with ten or more employees must provide a warning before knowingly and intentionally exposing their employees or the public to an amount of the listed pesticide that poses a significant risk. The warning must be "clear and reasonable." Also, 20 months after a pesticide is listed, businesses must not knowingly discharge listed pesticides, in a concentration that poses a significant risk, into drinking water or onto land where it will pass or probably will pass into a source of drinking water.

When does a warning need to be given?

Unless it can be demonstrated that exposure to a chemical listed under Proposition 65 as known to cause cancer (such as a pesticide) poses "no significant risk," a warning must be provided. Businesses may choose to provide a warning based on the presence of the pesticide without attempting to evaluate the exposure. If a substance is listed because of its carcinogenicity, the "no significant risk" level is defined as "the level which is calculated to result in no more than one excess case of cancer in 100,000 individuals exposed over a 70-year lifetime." In other words, if someone is knowingly and intentionally exposed to a listed substance (including a pesticide on the list) at or above this level, they must be warned of a cancer risk.

If a substance is listed as a reproductive toxicant, the level of exposure that triggers the Proposition 65 warning requirement is defined as the level at which there are no observable effects, divided by 1,000. That is, the level of exposure is the "no observable effect level" divided by 1,000. The "no observable effect level" is the highest dose level that is not observed to cause reproductive harm in humans or test animals.

In what form must Proposition 65 warnings be given?

For pesticide workplace settings, meeting the requirements of DPR's hazard communication regulations governing pesticide and worker safety requirements also meets the warning requirements of Proposition 65 regarding warnings for employees. Proposition 65 regulations also allow warnings to be provided in the same manner as they are provided under the federal Hazard Communication Program regulations for workplace exposures.

The State hazard communication program requires that, whenever employees are working in treated fields or handling pesticides, the employer must display Pesticide Safety Information Series (PSIS) leaflet A-9 ("Pesticide Safety Rules for Farmworkers"), PSIS A-8 ("Safety Rules for Pesticide Handlers on Farms"), or PSIS N-8 ("Safety Rules for Pesticide Handlers in Non-Agricultural Settings") at the work site or at a central location where workers gather. The leaflets (available online in English at and Spanish at, and Punjabi at specifically discuss Proposition 65. It must be read upon request to any employee. In addition, application-specific information identifying the pesticide, location of the treated area, restricted entry interval, and crop or site treated must be displayed at a central location within 24 hours of the application and remain for 30 days or until field workers are no longer present, whichever occurs earlier. PSIS leaflets and application-specific information provide a warning comparable to those provided for other occupational exposures under the Hazard Communication Standard and may be superior to the "generic" safe harbor warning signs authorized by Proposition 65 regulations.

For exposures to the general public, the warning may be given by a variety of means, such as labeling a consumer product, posting signs in affected areas, sending notices to affected residents, or publishing notices in a newspaper. For instance, signs can be found on most gas pumps; and some utility companies include warning notices in their billings. In some instances the companies comply with Proposition 65 by removing the chemicals in question from their products.

How is Proposition 65 enforced?

Proposition 65 is enforced through civil lawsuits. Lawsuits may be initiated by the State Attorney General, any district attorney, and some city attorneys (those in cities with a population exceeding 750,000). In addition, lawsuits may be initiated by private parties acting in the public interest, but only after providing notice of the alleged violation to the business accused of the violation with copies of the notice to the Attorney General and the appropriate district attorney. The notice must provide adequate information to allow the recipient to assess the nature of the alleged violation. A notice must comply with the information and procedural requirements specified in the regulations. A business found guilty of violating Proposition 65 may face penalties of up to $2,500 per day for each violation. In addition, the business may be ordered by a court to stop committing the violation.

For more information about Proposition 65, contact the OEHHA office at (916) 445-6900, For information about compliance with the Hazard Communication Program for work sites where pesticides are used, contact your county agricultural commissioner's office or the Department of Pesticide Regulation at (916) 445-4300,